1. Field of the Invention
The present invention relates to compositions and methods of making security inks for use in inkjet printers.
2. Description of Related Art
As printing technology has advanced and printers became readily available to the public, more and more documents began to be printed on demand. The inherent value of some of these documents, such as personal checks, stocks, bank notes, wills, deeds and drug prescriptions, enticed counterfeiters to alter or duplicate them.
Most printing systems print by placing an ink or toner on a surface of a substrate where it stays and forms an image. Some inks and toners are relatively easy to remove from the substrate surface by scratching them off or by using solvents. These documents are easy targets for forgery.
Systems have been developed over the years to prevent this type of document alteration. For example, U.S. Pat. No. 1,727,912 to Snyder discloses a form of paper that can be used for protecting the integrity of information printed on it. The paper includes a coating with relatively low ink absorption properties and a body that readily absorbs the ink. A secure document is created by slitting or rupturing the coating during a writing process so that the ink penetrates into the absorbent body of the paper. Once the ink has been absorbed, it is difficult to remove. This specialized paper is expensive due to the materials and manufacturing methods required to make it.
U.S. Pat. No. 5,124,217 to Gruber et al. discloses a secure printing toner for electrophotographic printing. When exposed to toluene, a popular solvent often used in document forgery, the toner produces a color stain indicating an attempted forgery.
U.S. Pat. No. 7,220,524 to Heilman et al. discloses a color penetrating toner usable in laser printers. The toner is typically used with a substrate having a special coating for aiding penetration. After penetration, the toner printed images are difficult to remove.
There is a need for a relatively inexpensive penetrating ink usable in an inkjet printer that provides desirable penetration characteristics for providing the extra security features for the documents.